Battery Historian & Energy Profiler | Android System Design

Battery Historian is Google's web-based tool for visualizing Android battery usage data. The Energy Profiler in Android Studio provides in-session energy estimates. Together they tell you exactly which of your app's activities are consuming battery.

Android Studio Energy Profiler

Access: Run → Profile App → select "Energy" tab.

The Energy Profiler shows:

CPU usage — correlated with your code activity
Network activity — radio wake events
Location usage — GPS/network location requests
Wake lock state — when your app holds the CPU awake

Reading the profiler:

Timeline ──────────────────────────────────
CPU      ░░░░████░░░░░░░████████░░░░░
Network  ░░░░████░░░░░░░░░░░░░░░░░░░
Location ░░░░░░░░░░░████████░░░░░░░░
Wake lock ████░░░░░░░░░░░████░░░░░░░
Energy    Low────────────High────────

Long Network bars paired with short CPU usage indicates background network polling — expensive and avoidable.

Battery Historian Setup

Battery Historian runs in Docker:

# Install Docker, then:
docker run -d -p 9999:9999 gcr.io/android-battery-historian/stable:3.1 --port 9999

# Or use the web version at: https://bathist.ef.lc/

Capturing Battery Stats

# Step 1: Reset stats to get a clean baseline
adb shell dumpsys batterystats --reset

# Step 2: Disable charging (or use adb to simulate)
adb shell dumpsys battery unplug

# Step 3: Run your app / usage scenario (10–30 minutes)

# Step 4: Export battery report
adb bugreport > /tmp/bugreport.zip

What to Look For in Battery Historian

Wakelock abuse:

KEY NAMES: wakelock_in
Pattern: Frequent short wakelocks = polling loops
Fix: Move to push (FCM) or WorkManager with constraints

Mobile radio activity:

KEY NAMES: mobile_radio, data_conn
Pattern: Frequent ON/OFF toggles = un-batched network
Fix: Batch requests; use OkHttp caching

GPS/location:

KEY NAMES: gps, scan_wifi
Pattern: GPS active when app is background = location leak
Fix: Remove updates in onStop; use geofencing for background

Identifying Battery Drains Programmatically

// Check if your app is in App Standby "Restricted" bucket
val usageStatsManager = getSystemService(Context.USAGE_STATS_SERVICE) as UsageStatsManager
val isRestricted = usageStatsManager.appStandbyBucket == UsageStatsManager.STANDBY_BUCKET_RESTRICTED

// Check battery optimization exemption status
val powerManager = getSystemService(Context.POWER_SERVICE) as PowerManager
val isIgnoringBatteryOptimization = powerManager.isIgnoringBatteryOptimizations(packageName)

Wakelocks: Audit and Fix

// ❌ PowerManager WakeLock not released — device stays awake
val wl = powerManager.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "MyApp:sync")
wl.acquire()
// ... work that might throw, leaving wl unreleased

// ✅ Always use try/finally; or use timeout
wl.acquire(60_000)  // auto-release after 60 seconds maximum
try {
    doSync()
} finally {
    if (wl.isHeld) wl.release()
}

Battery Stats adb Shortcut

# Quick wakelocks summary without full bugreport
adb shell dumpsys batterystats | grep "Wakelock"

# Network usage by app
adb shell dumpsys netstats detail

# Top battery consumers
adb shell dumpsys batterystats --charged | grep "Estimated power use"

Common Battery Offenders

Offender	How to spot	Fix
Unreleased WakeLock	Battery Historian wakelock row never drops to 0	`acquire(timeout)` + `finally { release() }`
Background polling	Rapid network spikes while screen off	Replace with FCM push
GPS in background	Location row active when no user visible feature	Remove location updates in `onStop`
Excessive JobScheduler jobs	Many short `job` events in historian	Batch into fewer, longer jobs
Unregistered sensor listener	CPU row consistently active in background	Unregister in `onStop`